There is well known multistage fuel injection control of an engine that fuel injection at a plurality of times is performed in one cycle. According to the multistage fuel injection control, combustion can be performed actively so as to reduce combustion noise and exhaust emission. Post-injection control is performed mainly for the purpose of burning particulate matter accumulated in a diesel particulate filter (DPF) or increasing exhaust energy so as to improve acceleration at low speed and small load. The Japanese Patent Laid Open Gazette 2007-162585 discloses construction of an engine in which the post-injection control is performed so as to reclaim the DPF.
However, the post-injection control causes bore flush when injection amount is excessive, thereby being not materialized as fuel injection control. Bore flush is a phenomenon that occurs when fuel collides with a wall surface of a cylinder so as to remove an oil lubrication layer or when fuel is accumulated in an oil pan. Then, the post-injection control performed in a wide range of an operating region for increasing the exhaust energy has not been realized.